From: Alex Young <alex@...>
Date: 2007-08-02T04:19:40+09:00
Subject: Re: Performance diffrence between ifs and case

dblack@rubypal.com wrote:
> Hi --
> 
> On Thu, 2 Aug 2007, Alex Young wrote:
> 
>> Gregory Brown wrote:
>>> On 7/31/07, Paul <Paul.McArdles@gmail.com> wrote:
>>>> def nop
>>>> end
>>>>
>>>>
>>>> Benchmark.bmbm(20) do |x|
>>>>    x.report("range"){for i in 0..1000000 do nop end}
>>>>    x.report("times"){1000000.times do nop end}
>>>>    x.report("each"){(0..1000000).each do nop end}
>>>> end
>>>> ------------------------------------------------
>>>> range     0.657000   0.000000   0.657000 (  0.656000)
>>>> times     0.609000   0.000000   0.609000 (  0.609000)
>>>> each      0.594000   0.000000   0.594000 (  0.594000)
>>>> ----------------------------- total: 1.860000sec
>>>>
>>>>          user     system      total        real
>>>> range     0.641000   0.000000   0.641000 (  0.640000)
>>>> times     0.594000   0.000000   0.594000 (  0.594000)
>>>> each      0.578000   0.000000   0.578000 (  0.594000)
>>>
>>> I'll remember this next time I want to save 0.03 s per 1000000 
>>> iterations.
>>>
>>> <groans>
>>>
>>> My original point was that if you want to do something n times, use 
>>> n.times
>>> :)
>>>
>> My point was going to be that the one place optimisation really 
>> matters is in benchmark code - you only want to measure the effect 
>> you're looking for - but I managed to shoot myself in the foot and 
>> prove another point.  Don't assume, measure!  :-)
> 
> Even if one of the iterators (each or times) was much faster than the
> other, as long as you use the same one every time you're controlling
> for that.  You just wouldn't want to go back and forth.
'Tis true, 'tis true.  It was not my finest hour :-)

-- 
Alex